Known measurements show that the classical radius of an atom and nucleus is on the order of 10^-10 m and 10^-15 m respectively, while the radius of an electron does not exceed 10^-16 m, that is, if we enlarge the radius of an atom to 1 km (1000 m), then the radius of the nucleus within the atom is only 1 centimeter, and the radius of the electron will not exceed 1 millimeter.
It can be seen that the interior of the atom is ridiculously empty, and we can also imagine that if all the space inside the atom is "squeezed" so that the nucleus and electrons are close together, the density of matter will be very high. In fact, such a density is actually the density of a neutron star.
According to scientists' observations, a typical neutron star has a mass between 1.35 and 2.1 times the mass of the Sun, a radius of 10 to 20 kilometers, and an overall average density estimate of between 8 x 10^13 grams and 2 x 10^15 grams, that is, according to the highest estimate, a neutron star of 1 cubic centimeter can weigh 2 billion tons, while even the lowest estimate of a neutron star of 1 cubic centimeter has 80 million tons.
To put it simply, neutron stars are actually the dense cores left after the demise of those massive stars, and the nuclear fusion reactions inside them have long been stopped, and under the compression of their own strong gravity, the electrons in the matter of neutron stars have long been pressed into the nucleus, and combined with the protons in the nucleus to form neutrons, these neutrons and the neutrons that already exist in the nucleus are closely together, forming a powerful "neutron degeneracy pressure", and the neutron star is to compete with its own gravity, and then maintain the stability of its own form.
So if you ask what happens to a person who falls on a neutron star, the answer is obvious: in such a strong gravity environment, there is no chance that this person will survive. In order to get a more intuitive understanding of how terrible neutron stars really are, we can simply calculate how much gravity a person will experience on the surface of a neutron star.
The gravitational force (F) on the surface of a planet can be calculated by the formula "F = mg", where m represents the mass of the object, g is the gravitational acceleration on the surface of the planet, and the gravitational acceleration (g) can be calculated by the formula "g = GM/r^2", where G, M, and r represent the gravitational constant, the mass of the planet, and the radius of the planet, respectively.
Knowing that the mass of the Sun is about 1.9891 x 10^30 kilograms, for the sake of calculation, we might as well take the weight of this person as 70 kilograms, the mass of the neutron star as 1.5 times the mass of the Sun, the radius of the neutron star as 15 kilometers, and the gravitational constant as 6.67 x 10^-11.
For comparison, the Pyramid of Khufu is the largest known pyramid of ancient Egypt, according to researchers' estimates, this pyramid is about 6.84 million tons, and we all know that the g value of the earth is about 9.8, from which it can be calculated that the gravity of the pyramid of Khufu on the surface of the earth is about 67 billion newtons.
In other words, for a person weighing 70 kilograms, the gravity on the surface of a neutron star is roughly equivalent to the weight of 925 Pyramids of Khufu when he was on Earth.
Such a terrible gravity, even atoms are unbearable, so if a person falls on a neutron star, all the atoms that make up him will be crushed, and then become a large number of nuclei and electrons, but because the gravity on the surface of the neutron star is not enough to press electrons into the nucleus, these nuclei and electrons can be retained, and they will become part of the shell of the neutron star.
It is worth mentioning that, after all, neutron stars used to be the hot cores of massive stars, and in the process of neutron star "birth", it will also be accompanied by a very powerful "supernova explosion", so the temperature of neutron stars at the time of "birth" is actually very high, and its core temperature can reach 10^11 to 10^12K (Kelvin).
Even after a long period of cooling, their temperatures are still surprisingly high, and observational data show that the surface temperature of known neutron stars can usually reach hundreds of thousands of K, and some can even reach millions of K, while the surface temperature of the Sun is only about 5780K. So for these high-temperature neutron stars, people are vaporized long before they fall on their surface......
(↑ Nearest Neutron Star)
Of course, this is not an imaginary discussion, in fact, such a thing cannot happen at all, you must know that even the nearest neutron star is 400 light-years away, this neutron star is called "RX J1856.5-3754", which is located in the southern corona in the sky, so we don't have to worry about the threat of neutron stars at all.